Fiber optic connectors have long been used to join an optical fiber to another optical fiber or to a fiber optic component such as a light emitter, a light detector or an optical switch. Exemplary light emitters include laser diodes and light-emitting diodes. Exemplary light detectors include PIN photodiodes, integrated detector/pre-amplifiers (IDPs), and avalanche photodiodes (APDs).
Fiber optic connectors for connecting individual fiber optic fibers have been widely commercialized and typically include an alignment sleeve. Many connector devices have also been developed for physically mating the parallel faces of a bundle of fiber optic fibers. Simple mechanical splices have also been used, such as a capillary splice, fusion splice or epoxy connection. These types of fiber optic connectors all add loss to the fiber optic communication system to which they belong.
Simple fiber optic connectors and splices join two fiber ends together. By way of contrast, other types of passive fiber optic coupling devices are used where three or more optical fibers are to be joined. Fiber optic couplers split optical signals into multiple paths or vice versa. Splitters, tap ports, switches, wave guides, and wave-length-division multiplexers (WDMs) are also used to divide or combine multiple optical signals.
An optical signal consisting of a flow of photons is similar to an electrical signal in some respects. However, an optical signal does not flow through a receiver to ground. Instead, an optical signal flows to a detector where it is absorbed. If multiple fiber optic receivers were connected in series, no optical signal would reach beyond the first receiver. Therefore, multiple optical ports must generally be parallel and allowances must be made for reduction in optical signal strength due to signal division and attenuation losses that result from refraction index differentials, fiber end misalignments, spacing between fiber ends, and imperfections in the fibers at the junctions.
In the telecommunications industry, large numbers of fiber optic communication modules with fiber optic inputs and/or outputs are frequently removably mounted in vertical enclosures or racks. These enclosures or racks sometimes have common vertical backplanes into which the fiber optic communication modules, such as routers, are plugged. The fiber optic communication modules are designed to be rapidly removed and replaced to facilitate repairs and upgrades and minimize any negative impacts on the speed, capacity and/or reliability of the overall telecommunications system. Quite clearly it is necessary to provide some means for physically supporting many parallel fiber optic fibers leading to such rack-mounted fiber optic communication modules while at the same time ensuring accurate mating of the ends of the fibers with a minimum of signal losses. Simply using a conventional fiber optic connector for each optical fiber is undesirable due to the expense of such connectors and the relatively large amount of space that is occupied by such connectors. Furthermore, conventional fiber optic connectors usually cannot be rapidly connected and disconnected.
Complex and expensive backplane assemblies have been developed which combine an electrical backplane with a fiber optic backplane. A plurality of individual connector openings are provided in the optical backplane for receiving individual fiber optic connectors that are arranged in rows. See, for example, U.S. Pat. No. 5,980,312 of Chapman et al. Multiple optical fibers have also been mounted in parallel fashion through a supporting planar substrate, but the ends of the fibers must still be individually connected.
Electronic assemblies that utilize components mounted on a conventional circuit board rely on a conformal material to insure electrical contact between the input/output leads of the components with conductive traces or paths on the circuit board. Typically this conformal material is solder, an alloy of tin and lead that becomes liquid when heated to a relatively low temperature. Solder re-flow is thus used to fill any gaps between the component leads and the circuit board traces, while at the same time providing mechanical and electrical interconnections. At ambient temperature, the solder remains solid and provides the required electrical conductivity. Equivalent optical assemblies utilizing conventional optical interconnects require precisely mated optical waveguides to form the optical paths. At present, a low cost automated optical interconnect analog to soldered PC board connections does not exist. Unlike the connection of individual copper wires to a circuit board, the connection of an optical fiber to a fiber optic transmitter or a fiber optic receiver requires tedious, cut, polish and alignment procedures.